The term C-076 is used to describe a series of compounds isolated from the fermentation broth of a C-076 producing strain of Streptomyces avermitilis. The morphological characteristics of the culture are completely described in copending U.S. application Ser. No. 772,601 filed Feb. 28, 1977, now abandoned. The C-076 compounds are a series of macrolides, each of which has substituted thereon at the 13-position, a 4-(.alpha.-L-oleandrosyl)-.alpha.-L-oleandrose group. The C-076 compounds have a very high degree of anthelmintic, insecticidal, ectoparaciticidal and acaracidal activity.